Let’s face it: your cellphone is literally covered in germs.
You’re on it all the time, and it goes basically everywhere with you (including the bathroom). It’s disgusting. Studies have shown that most phones test positive for potential disease-causing microbes and fecal matter (so yeah, poop). And because you’re constantly touching your phone, all that grossness can get transferred right back to your face.
TL;DR — your phone is a mobile germ carrier.